The invention relates to print media with a near infrared sense mark and apparatus which employ them. The near infrared sense mark triggers an automated operation such as printing, advancing, cutting and/or dispensing a print medium. Particular embodiments include print media and apparatus for point-of-sale transactions such as cash registers, automated teller machines and other receipt generating equipment.
Conventional business machines such as cash registers, ticket dispensers and automatic teller machines typically employ sense marks in dispensing printed media. This typically includes printing, advancing, cutting and stopping the print medium. Black colored marks are the most commonly used sense marks employed in business machines for dispensing printed media. One major disadvantage of using black sense marks is that the area between the sense marks must be clear for proper processing. This greatly reduces the area available for commercial, advertising and promotional printings. Although this overall technology is quite reliable, some sporadic problems do result when thermal papers are used. The thermal dyes on the thermal papers between sense marks can be prematurely activated and darkened during handling, storing or processing, causing a malfunction in the automatic operation of the business machine.
Replacing the black sense marks with other types of marks has not been successful. Use of other colors has resulted in either lower reliability or high cost. Similarly, the use of transparent marks that fluoresce when exposed to UV light has resulted in low reliability due to background interference from the substrate (paper) which contains UV absorbing and/or fluorescing compositions. This minimizes the contrast between the mark and the base sheet.
Near infrared fluorescent (NIRF) compounds have been used for marking articles for identification/authentication purposes Examples include U.S. Pat. No. 5,292,855, issued Mar. 8, 1994, U.S. Pat. No. 5,423,432, issued Jun. 13, 1995; U.S. Pat. No. 5,336,714, issued Aug. 8, 1994; and U.S. Pat. No. 5,703,229. issued Dec. 30, 1997, to Krutak et al. Other examples include U.S. Pat. No. 5,614,008, issued Mar. 25, 1997, to Escano et al.; and U.S. Pat. No. 5,665,151, issued Sep. 9, 1997.
The use of NIRF compounds is complicated by the fact that they are generally not stable in air. Krutak et al. disclose incorporating the NIRF compounds in carrier polymers and incorporating NIRF compounds in copolymers to protect the NIRF compounds from oxidation (see U.S. Pat. Nos. 5,292,855 and 5,703,229).
U.S. Pat. No. 5,682,103, issued to Burrell on Oct. 27, 1997, discloses an apparatus and method for checking the authenticity of security documents, wherein near infrared or visible waves are emitted and directed to the document. A detector detects any emitted near infrared or visible waves reflected from the document. This method and apparatus detects electromagnetic particles such as stainless steel fibers within the base material of a document to determine its authenticity.
Inks with photochromic or fluorescent pigments and layers which fluoresce or change color when exposed to a light source other than ambient light are typically referred to as optically variable inks. Such inks are used to provide latent images as a security feature. These optically variable inks allow for non-destructive testing of the security feature, allowing the printing of such inks to be monitored. Such optically variable inks typically respond to infrared or ultraviolet light. An example of an aqueous printing ink for jet printing which fluoresces under ultraviolet radiation is described in U.S. Pat. No. 4,153,593. The dyes described in this reference are water soluble and include fluorescein, eosine dyes and Rhodamine dyes. Representative disclosures of other inks include U.S. Pat. No. 4,328,332, issued to Hayes et al. on May 4, 1982, and U.S. Pat. No. 4,150,997, issued to Hayes on Apr. 24, 1979.
Unlike marks used as security features, a sense mark defines a location on the print media to trigger an automatic operation. To accomplish this, the sense mark must not only achieve a threshold emission such that it is sensed by a photon detector, it must achieve sufficient contrast with the base substrate such that its location can be identified by a logic apparatus via signals from the photon detector. Security features do not require such a level of contrast with the base sheet. The security marks need only be sensed for a pass/fail test. While interference with the base sheet for a security mark cannot be ignored, the location of the mark is typically irrelevant, such as where the NIRF compound is incorporated in the base sheet or is incorporated in the printed matter itself.
Many business machines operate with thermal paper. The use of direct thermal paper complicates the availability of a sense mark. Direct thermal paper is a thermosensitive recording material upon which print or a design is obtained by the application of heat energy, without an ink ribbon. Direct thermal paper comprises a base sheet and a coating. A major distinction in thermal paper from other coated papers is that special color forming chemicals and additives are present in the coatings such that, when heat is applied by a thermal head, the color forming chemicals react to develop the desired print or image.
The most common type of thermal coating is that of a dye-developing type system. The three main color producing components in a dye-developing-type thermal paper are colorless dye (color former), a biphenol or an acidic material (color developer) and sensitizer. These solid materials are reduced to very small particles by grinding and are incorporated into a coating formulation along with any optional additives such as pigments, binders and lubricants. This coating formulation is then applied to the surface of a base sheet or other support system and dried.
Where security features or sense mark is desired for thermal paper, the inks must not pre-react the reactive components within the thermal sensitive coating of the thermal paper to detract from the thermal papers printing performance. Certain chemical factors can adversely affect and degrade the performance of the thermosensitive coating and should be avoided such as some organic solvents (ketones), plasticizers (polyethylene glycol-type), amines (ammonia) and certain oils (soy oil). The coating solutions for NIRF compounds typically contain amines and other compounds, which the thermosensitive coatings react with.
To protect thermal paper from environmental conditions and premature coloration from handling, a number of developments have been made. One is to produce a barrier or protection layer on top of the thermal coating (see U.S. Pat. Nos. 4,370,370; 4,388,362; 4,424,245; 4,444,819; 4,507,669; and 4,551,738). Another approach is to encapsulate the reactive components and microcapsules which rupture or are permeable when exposed to heat. See U.S. Pat. Nos. 4,682,194; 4,722,921; 4,742,043; 4,783,493; and 4,942,150. These protection measures are not reliable in preventing premature coloration of the thermosensitive layer when exposed to a NIRF coloring solution.